This proposal is to conduct an analysis of the relationship between exposure to N-nitroso compounds (NOC) and risk of adult and childhood brain tumors. A comprehensive database of indices of NOC exposure from both dietary and non-dietary sources ill be developed. This will be used in conjunction with data collected in two completed international multicenter case- control studies of adult brain tumors (number of cases equal 2,017) and childhood brain tumors (number of cases equal 1,351) to test the hypothesis that exposure to NOC increases risk of both types of brain tumor. These are the largest epidemiologic studies to date of brain tumors, and were specifically designed to focus on the NOC hypothesis. Subsequent to a central review of histologic slides for cases, numbers will be sufficient to permit histological specific analyses for several tumor types. The proposed study will permit a direct comparison of the role of NOC in childhood and adult brain tumors. Identification of NOC as an important risk factor for brain tumors could lead to directly implementable prevention strategies, because the main source of human exposure to NOC is from endogenous formation following ingestion of specific foods with a high concentration of such precursors as nitrite compounds.